No, watts per gallon is irrelavent. There is no 24" 48w bulb. You'd need a 2x24w T5HO for that. That's what I would recommend anyways... or a 1x24w T5HO if you can get one. I'd just run an actinic on a 2x fixture until you're ready to go high tech.

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-Jonathan

"What, exactly, is the internet? Basically it is a global network exchanging digitized data in such a way that any computer, anywhere, that is equipped with a device called a 'modem', can make a noise like a duck choking on a kazoo." - Dave Barry

Not true ... I really don't like when websites give such blanket statements. High maintenance / light plants do need a high WPG .. but there are a few low light plants that do fine in less than 1.0 WPG.

Also ... from what I've read ... the WPG rule kind of goes out the window when dealing with higher output bulbs like T5HO bulbs. The link below I think provides a better way to detemine a tank's light level.

I'm into pretty simple "water keeping" and watts per gallon is a good starting point. If you keep low light, low tech (no CO2) tanks, you can grow low light plants with less than a watt of light per gallon of tank volume. In your tank, a 24 inch, 15 watt, 6500 K bulb will grow Java fern, Anubias, Pennywort, Cryptocoryne, Singapore moss and some of the less light demanding Amazon swords. If you get a little creative and float a small piece of driftwood, you can attach some Water sprite and Banana plants to it and they'll grow nicely.

Change out half the tank water every week and dose a good fert and you'll have a well planted tank in no time.

B

__________________"Fear not, my young apprentice. Just change the tank water."

WPG in reference to anything but plain-jane fluorescent lights is pretty pointless.

That being said- many plants do just fine with less than that old formula. Add to the mix, T5 and T5-HO which provide mire usable light per watt and things get tricky.

1 WPG of T5HO is considerably more usable light output per watt.

When I go serious about plants in my 29g, I picked up a twin bulb T5 HO fixture. With both bulbs on (using a timer), plants took off, but so did the Black Beard/Brush Algae and Staghorn algae. I had to get really aggressive with Flourish excel and then added DIY CO2 to deal with it. I cut back to one bulb and plants slowed down a bit (though still healthy growth), and the BBA/Staghorn issue also went away).

The more light, the more nutrients your plants will need- from the macros (NPK) to micro nutrients and CO2...